The conventional method of orthodontic tooth movement, as practiced in the prior art, has been one of constant heavy or light pressure applied to the tooth in order to move the tooth through the adjacent bone. Constant pressure applied to the periodontal membrane by traditional orthodontic appliances causes the periodontal fibers to become cell-free which results in standstill of the tooth. Compression of tissue results in reduced blood supply and tissue necrosis, and the tooth will not move again until the bone subjacent to the hyalinized tissue has been eliminated by undermining resorption. Generally, it is essentially the magnitude of the force which will determine the duration of the hyalinization. Moreover, strong forces produce a wide hyalinization area of long duration. A discussion of this phenomenon may be found on pages 76 and 97 of Current Orthodontic Concepts and Techniques, T. M. Graber, Editor, published by W. B. Saunders & Co., 1969.
When a tooth is tipped by a continuous force exerted on it by the usual prior art orthodontic appliance, the periodontal membrane is compressed in a circumscribed area situated close to the alveolar crest. This area becomes cell-free and blood vessels are occluded. A description of this occurrence may be found, for example, at Page 497 of Orthodontic Principles and Practice by Graber, 2d Edition, published by Saunders & Co., 1967. If the pressurized area of the periodontal membrane during the movement of a tooth by an orthodontic device is not compressed by strong forces, then the formation of oesteoclasts, the cells responsible for resorption of bone, will be enhanced. The flow of blood to the area will not be restricted, and consequently oesteoclastic activity will become more vigorous and bone resorption will be increased.
Various orthodontic appliances are described and claimed in U.S. Pat. Nos. 4,123,844; 4,244,688 and 4,229,165, all of which have issued in the name of the present inventor, which introduce pressure impulses to the teeth being moved, rather than a continuous pressure. With every pressure impulse, the tissue pressure in the periodontal membrane and adjacent bone tissue will be increased. When the pressure is relaxed, the tissue fluid in the periodontal membrane and adjacent bone tissue will be reduced. This fluctuation from high pressure to low pressure in the periodontal and adjacent tissue will result in a pump-like action that will suck blood and tissue fluid into the area, and which will then expel fluid from the area, for each cycle of operation. This pulsation action serves to increase the cellular activity around the moving tooth, giving rise to more oesteoclasts for bone resorption and more oesteoblasts for bone apposition.
The active exchange of fluid during the pulsating operation of the appliances described in the patents helps to carry the by-products of bone resorption out of the resorption area. The pulsating tooth movement produced by such vibrational appliances in physiological and dynamic in nature, rather than pathological. Beacuse the pulsation pressure exerted by the appliances described in the patents does not result in areas of hyalinization and necrosis, there is no root resorption or horizontal bone loss during the operation. The pump-like action of the tooth being pulsed by the appliances described in the patents is the same on the tension side of the tooth as on the compression side, but opposite in the timing cycle. On the tension side of the tooth, the increased blood supply results in increased cellular activity.
The vibrational assembly of the present invention is constructed to produce the same pulsations as are produced by the systems described in the patents referred to above. However, vibrations are produced in the assembly of the present invention by a radio transmitter which radiates radio waves to a radio receiver mounted on an orthodontic appliance, or directly on the patient's tooth. The radio receiver responds to the radio waves from the transmitter to cause its speaker to vibrate and set up the desired vibrations for the tooth or teeth being treated. The receiver may be mounted, for example, on the external or internal bow of a headgear, or other orthodontic appliance, or, as noted above, the receiver may be mounted directly on the tooth being treated.
The frequency and amplitude of the speaker vibrations can be easily controlled by controlling the frequency and amplitude of the radio wave radiated by the transmitter. The transmitter itself may be kept in the same room as the patient, or carried by the patient when he is out of doors.
The effect of the radio wave radiated by the transmitter is to excite the speaker associated with the radio receiver, causing the speaker to vibrate. The vibrations of the speaker are introduced into the tooth or teeth being treated.
As mentioned above, the radio receiver may be mounted on an orthodontic appliance, or it may be made small enough to be mounted directly on the tooth being treated by means, for example, of a suitable adhesive, or on a metal band which is fixed to the tooth. Moreover, the radio receiver and speaker may be mounted on an orthodontic positioner, for example, of the type described in U.S. Pat. No. 4,123,844, to assist the normal action of the positioner.